[delayed_job4] Update dj.erb

[radamanthus]

Backport changes made in V5 to improve worker termination

• Make sure DJ workers do not become orphans (https://github.com/engineyard/ey-cookbooks-stable-v5/pull/224)
• Add a check for zombie DJ workers (https://github.com/engineyard/ey-cookbooks-stable-v5/pull/251, https://github.com/engineyard/ey-cookbooks-stable-v5/pull/265)

[radamanthus]

This fixes #345

[jegasega]

Description of your patch

• Ensure that dj worker processes do not become orphans
• Add a check for zombie DJ workers

Recommended Release Notes

Ensure that dj worker processes do not become orphans

Estimated risk

Low

Components involved

DelayedJob custom chef recipe

Description of testing done

See QA instructions

QA Instructions

Test on configuration A_dj

Configuration A rails_activejob_example (delayed_job branch) App Unicorn Ruby 2.3 RubyGems 2.6.4 Postgres 9.4 US East Virginia Solo

Boot the test environment under the QA stack Enable the delayed_job recipe. Modify the recipe to install DelayedJob on the solo instance Modify the recipe and set a very low worker memory limit (e.g. low enough to always trigger the memory limit even with zero workload, e.g. 10MB). Upload custom cookbooks to the environment Run chef Observe the delayed_job processes by running ps -ef | grep elay Make sure:

• monit is terminating the DelayedJob process
• new workers are being started
• no orphan processes are being left behind

[jegasega]

Tested the pull request against provided testing procedure. Everything works like expected. LGTM from my side.